A function which calls itself or is in a potential cycle of function calls

For Example:

Scenario: An Evens number is an integer whose digits are all even. For example 2426 is an Evens number but 3224 is not.

Write a function named isEvens that returns 1 if its integer argument is an Evens number otherwise it returns 0.

The function signature is int isEvens (int n).

Solution:

using System;

namespace evenNumber
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Enter Integer Value");
            string input = Console.ReadLine();
            int Evens = Convert.ToInt32(input);
            int a = isEvens(Evens);
            Console.WriteLine("value return:   " + a);
            Console.ReadLine();           
        }        
        private static int isEvens(int n)
        {
            int a = n % 10;
            n = n / 10;
            if (a == 0 || a == 2 || a == 4 || a == 6 || a == 8)
            {
                if (n == 0)
                {
                    return 1;
                }
                else
                {
                   return isEvens(n);
                }
            }
            else
            {
                return 0;
            }

        }
    }
}

In above example, isEvens(n) function called itself.

Output: